Serving for the King
Several Royal Guards were present when T'Challa's returned to Wakanda. During his coronation ceremony, the King's guards were in attendance to witness their next king be challenged by M'Baku. T'Challa claimed victory, thus the Royal Guard swore fealty to the then crowned King T'Challa.
During Erik Killmonger's usurpation of the throne through traditional laws, the King's guard were bound by those same laws to obey the throne, which Killmonger then sat upon.
At the Battle of Mount Bashenga, only Royal Guard members loyal to Killmonger were present during the preparations for conquest and went into the fight against T'Challa and the Dora Milaje. However, upon W'Kabi's surrender to Okoye, they too stood down to surrender to the Dora Milaje.
In 2018, while preparations for the Black Order's incursion into Wakanda were made, the Royal Guard stood alongside the Border Tribe, the Dora Milaje, and the Jabari Tribe just on the periphery of the defense barrier keeping the Outrider vessels at bay. The Royal Guard stood in formation in proximity of their Black Panther, awaiting the return of Steve Rogers and Natasha Romanoff from speaking with Proxima Midnight and Cull Obsidian.
Once the siege of Outriders began to break through, King T'Challa ordered an opening of a narrow choke point to prevent enemy flanking. While the Royal Guard were able to slay many of the mindless creatures with their Sonic Spears, many were still killed by the large scale vessels in the Black Order's arsenal. Despite being overwhelmed and outnumbered, the armies of Wakanda still prevailed upon the arrival of Thor, Rocket Raccoon, and Groot, who destroyed the Outrider ships and a majority chunk of their forces.
Five years after Thanos' victory, Wakandans were caught unaware by the return of many of their fallen, including the royal heirs, returned by the efforts of the Avengers. However, before celebrations could be held, Doctor Strange appeared via astral form and appraised them of Thanos' attack. Strange sounded the clarion call to arms, projecting numerous Sling Ring portals across Wakanda to rally their forces against their once-nemesis and his armies.
Returned members of the Royal Guard thus joined in a united Wakandan army to aid the Avengers, and battled Thanos' forces. Many brave souls, both survivors and returned, perished in the conflict which ultimately ended in a resounding victory for the Avengers and their allies as Tony Stark sacrificed his life to end Thanos and the full of his forces with the Nano Gauntlet.
Some days later, the Golden City celebrated the return of the victims of Thanos' Snap, as well as mourned the fallen in the Battle of Earth. The Royal Guard continued protection of the Golden Tribe, who were overlooking from the palace at the renewed joy of their homeland.